The present invention relates to data storage, and more particularly, to storing data using a block-interleaved and error correction code (ECC)-encoded sub data set (SDS) format.
Tape and optical storage devices use very powerful error correction codes, such as product codes or concatenated codes, in conjunction with interleaving to provide a very high degree of data integrity. These error correction schemes typically use two ECCs as component codes. Two important burst-error performance measures for tape storage systems protected by these schemes are: 1) lateral width of an erroneous stripe which is still capable of being corrected (this is also known as “broken track correction” capability), and 2) longitudinal width of an erroneous stripe that is still capable of being corrected. A “broken” track generally refers to a track that cannot be read correctly due to a problem on the media itself and/or a problem with the readback channel, e.g., as a channel that does not detect data correctly because of some systematic problem with the head.
In the past, the error-correction power of these component codes was increased in order to increase the format efficiency of stored data, which is equivalent to decreasing storage overhead, and/or to improve the level of data integrity. However, these improvements were achieved by increasing the size of the overall codeword containing component code words, i.e., by increasing the size of the buffer that contains a data set, and more importantly, by weakening the broken-track correction capability. However, improvements in data integrity should not be achieved at the expense of a reduction in the capability to correct broken tracks along with an increase in buffer size.
Accordingly, it would be beneficial to have a data storage format that increases the format efficiency of stored data and/or improves the level of data integrity without increasing the size of the data set buffer and/or degrading the capability to correct broken tracks.